The tunneling industry has been looking for a reliable continuous Tunnel Boring Machine (TBM) mining system for decades. In typical/conventional soft ground tunneling using a shield machine, forward movement is stopped for installation of the segmental lining. This means that the advance cycle is the sum of excavation and segment installation, which often take equal amount of time. In rock tunneling, use of double-shield TBMs are on the rise due to the advantages they offer, mainly one pass tunneling where the final lining is installed. Since the excavation and segment installation is simultaneous for double shield TBM, the advance cycle is determined by the longer of either excavation or segment erection process. Often in medium to soft rock conditions, segment erection takes more time, thus adding to the time requirement for each advance cycle. Meanwhile, when grippers of a double shield TBM cannot operate, the machine works by locking the front and tail shield and operates as a single shield, thus the work cycle of single shield and same timing issues apply.
The proposed method in this invention, which involves a system of helical segments that are installed continuously as the TBM thrusts forward, addressing all the aforementioned concerns. The Helical segment system allows for uninterrupted segment erection as the machine continues to excavate. Nearly all the TBM's thrust cylinders are utilized in pushing against the segments, with the exception of those in the area of the segment that is being erected at any given time. This is expected to increase tunneling speed significantly, with the possibility to reach up to twice the daily advance rates in certain settings.